Power injectors are devices used to inject fluids at controlled and programmed rates or pressures into patients. Important uses include computed tomography (CT) and angiography, where radiopaque contrast medium is injected into a patient's vascular system to enhance diagnostic images. With power injectors, a motor-driven ram advances the plunger of a syringe under microprocessor control to provide control of injection parameters such as flow rate, volume and timing. Such injectors are often loaded with sterile empty syringes that are filled by drawing fluid from a supply into the syringe through the syringe nozzle by using the ram to draw the syringe plunger backward. In other situations, the injectors are loaded with prefilled syringes. In either case, the syringes used are typically disposed of after a single use.
In CT and angiography, a typical fluid delivery system includes a power injector loaded with a single use disposable syringe that is filled with the contrast medium or other fluid, and with a delivery tube connecting the nozzle of the syringe to the vascular system of the patient. The tubing, which is also typically single-use and disposable, is commonly connected to the syringe after the syringe is loaded into the injector. When the use of the syringe and tubing is completed, the spent syringe and the tubing are removed from the injector and disposed of. Spent syringes as well as the used tubing has the capability of dripping or leaking residual amounts of fluid. This dripping or leaking can fall upon the injector components, particularly the syringe holding structure and locking mechanism, where, if not cleaned, can cause contamination or interfere with the injector operation. Cleaning of the injector of spilled fluid is time consuming, detracts from the utilization of the equipment and is accordingly costly.
In the prior art, many injectors have been configured to support syringes that are loaded into holder structure on the injector from the rear. Such syringes are typically provided with rear end flanges by which the syringes are locked to the holder and held in position for the injector ram to be coupled to and drive the syringe plunger. The loading and unloading of such rear loading syringes has required the insertion and withdrawal of the syringe nozzle through a circular opening in a closed annular holder. Upon loading, when no tubing is connected to the syringe nozzle, inserting the nozzle through the opening from the rear presents little problem. However, removal of a spent syringe from such an injector has resulted either in the withdrawal of an entire length of tubing through the opening, possibly with its leading end open to drip fluid that remains in the tube on the injector parts, or in the need to disconnect the tubing from the syringe nozzle and the withdrawal of the open nozzle end through the opening, which also can drip fluid onto the injector parts. Capping the syringe or the tubing end and the wiping of excess drippage undesirably increases the handling involved and is an inconvenience. The act of disconnecting the tubing from the syringe also occupies the hands of an operator and can result in the release of residual fluid that can require a further clean-up task.
Inventors of the subject matter of the present application have previously solved the above problem for certain types of syringes by providing a front loading injector. A front loading injector is one in which a front loadable syringe is positioned in front of an opening in an injector holder and loaded into the holder by translating the syringe rearwardly, back end first, into the injector. With front loadable injectors, the nozzle of the syringe need not pass through the opening of the holder upon loading or unloading. Such an injector, which is described and illustrated in U.S. Pat. No. 5,279,569, which is assigned to the assignee of the present application, enables an operator to remove the syringe from the injector by translating it forwardly away from the injector, without removing connected injection tubing from the syringe nozzle. This configuration has resulted in the maintenance of the injector free from fluid contamination, and has provided easier injector usage, while saving operator and physician time.
However, not all syringes, and particularly not all prefilled syringes, can be easily made available in forms that can be loaded into injectors from the front. As a result, breach loading or rear loading injector holders are still provided for many applications. Rear loading injectors are injectors in which a rear loadable syringe is positioned behind a holder of the injector and translated, nozzle first through an opening in the holder until structure on the syringe, usually a flange or other outwardly extending element at the syringe rear, seats forwardly against the holder. Usually the holder opens for loading or unloading of a syringe by pivoting away from the injector housing, either in hinged or turret fashion. Such breach loading injectors still present the above described problems in connection with the removing of spent syringes and the connected tubing.
Breach loading injectors have existed in the prior art that are modified versions of the injector disclosed in U.S. Pat. No. 5,279,569, referred to above, with the syringe holding head structure replaced with a breach loading syringe holder that pivots out of the path of the ram so that a rear loading syringe can be loaded or unloaded from the rear of the holder. Such injectors have nonetheless possessed the same disadvantages in removing spent syringe and injection tubing assemblies possessed by other breach loading injectors of the prior art.
Accordingly, there remains a need for improvement in the removal of spent syringe and injection tubing assemblies from power injectors and to eliminate the handling and equipment contamination problems that have been characteristic of the prior art rear loading power injectors available for angiographic and computed tomography.